Optical novelty filter using bacteriorhodopsin film

Haloarchaea: worth exploring for their biotechnological potential

Halophilic archaea are unique microorganisms adapted to survive under high salt conditions and biomolecules produced by them may possess unusual properties. Haloarchaeal metabolites are stable at high salt and temperature conditions that are useful for industrial applications. Proteins and enzymes of this group of archaea are functional under salt concentrations at which bacterial counterparts fail to be active. Such properties makes haloarchaeal enzymes suitable for salt-based applications and their use under dehydrating conditions. For example, bacteriorhodopsin or the purple membrane protein present in halophilic archaea has the most recognizable applications in photoelectric devices, artificial retinas, holograms etc. Haloarchaea are also useful for bioremediation of polluted hypersaline areas. Polyhydroxyalkanoates and exopolysccharides produced by these microorganisms are biodegradable and have the potential to replace commercial non-degradable plastics and polymers. Moreover, halophilic archaea have excellent potential to be used as drug delivery systems and for nanobiotechnology by virtue of their gas vesicles and S-layer glycoproteins. Despite of possible applications of halophilic archaea, laboratory-to-industrial transition of these potential candidates is yet to be established.

Industrial and environmental applications of halophilic microorganisms

In comparison with the thermophilic and the alkaliphilic extremophiles, halophilic microorganisms have as yet found relatively few biotechnological applications. Halophiles are involved in centuries-old processes such as the manufacturing of solar salt from seawater and the production of traditional fermented foods. Two biotechnological processes involving halophiles are highly successful: the production of beta-carotene by the green alga Dunaliella and the production of ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid), used as a stabilizer for enzymes and now also applied in cosmetic products, from moderately halophilic bacteria. The potential use of bacteriorhodopsin, the retinal protein proton pump of Halobacterium, in optoelectronic devices and photochemical processes is being explored, and may well lead to commercial applications in the near future. Demand for salt-tolerant enzymes in current manufacturing or related processes is limited. Other possible uses of halophilic microorganisms such as treatment of saline and hypersaline wastewaters, and the production of exopolysaccharides, poly-beta-hydroxyalkanoate bioplastics and biofuel are being investigated, but no large-scale applications have yet been reported.

All-optical time-delay switch based on grating buildup time of two-wave mixing in a bacteriorhodopsin film

We demonstrate time-delay switches using the first-order dynamic diffraction light of two-beam coupled light with wavelengths of 632.8, 650, 532, and 488 nm in a bacteriorhodopsin film. The optimal wavelengths are selected and the relationship between incident intensity and delay time is discussed. A switch delay time ranging from 3.52 to 12.5 s is presented by the 632.8 nm wavelength, while a delay time ranging from 1.24 to 10.6 s is demonstrated by the 488 nm wavelength. On the other hand, the wavelengths of 532 and 650 nm are not suitable for time-delay switches due to the large variation of first-order diffraction intensity for lower incident intensities.

All-optical time-delay relay based on a bacteriorhodopsin film

Using the property of dynamic complementary suppression modulated transmission of bacteriorhodopsin film, we propose and demonstrate an all-optical time-delay relay in an incoherent light system. The relay can last for a certain amount of time after the switch function of turn off (or turn on) is activated. Furthermore, the delay time can be adjusted by changing the lifetime of the M state and the intensities of blue and yellow beams.

Relationship between parameters of bacteriorhodopsin film and behavior of optical novelty filters

To continue our earlier research on novelty filters in a system of incoherent light [Opt. Lett. 30,81 (2005)], we discuss the relationship between parameters of a bacteriorhodopsin film and the quality of a novelty filter image. For both fixed and moving velocities of the input image, differences in the novelty filter's image as a function of thickness, lifetime of the M state, and molecular concentration are displayed, and the optimal ranges of parameters of the bR film that correspond to the entire novelty filter image and obvious gray-level differences in the image are given. The method can be used to design high-quality novelty filter images in incoherent light systems.